The invention relates generally to the electrical system of an automotive vehicle and, more particularly, to the voltage regulator circuits of such systems.
Present day automotive voltage regulators are essentially single purpose circuits employed to regulate the output voltage of the vehicle alternator to within a narrow band of voltages corresponding to the rated battery voltage, under varying load conditions. Simply stated, the regulator provides a modulation of the field current of the alternator as a function of existing battery voltage which is continuously sensed for maintaining the rated voltage level.
Systems have been developed which employ the vehicle alternators to supply relatively high power at above normal voltage to auxiliary loads such as power tools and resistance heating wires embedded in window material for windshield deicing. To supply such high power, the alternator output voltage is usually increased. This has been accomplished in one approach by temporarily disconnecting the standard automotive load and the regulator from the alternator, and having the battery supply the load current during this period. In more recently developed systems, there is provided a dual regulation of the alternator output voltage, whereby the alternator output is regulated in accordance with both a substantially elevated alternator voltage and the voltage across the battery. To accomplish such dual voltage regulation, redesign of the voltage regulator circuitry has been necessary. Although, the redesigned circuitry has been generally successful, the requisite circuit modifications have required new regulator components and precluded the use or adaptation of standard, off-the-shelf voltage regulators where a dual regulation is to be achieved.